tornado singleton单例模式

class TOLoop:
    @staticmethod
    def instance():
        """Returns a global `IOLoop` instance.

        Most applications have a single, global `IOLoop` running on the
        main thread.  Use this method to get this instance from
        another thread.  To get the current thread‘s `IOLoop`, use `current()`.
        """
        if not hasattr(IOLoop, "_instance"):  //避免无意义的锁定， 因为大部分调用时只是简单的返回已经创建的_instance
            with IOLoop._instance_lock:
                if not hasattr(IOLoop, "_instance"):
                    # New instance after double check
                    IOLoop._instance = IOLoop()
        return IOLoop._instance

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tornado singleton单例模式

原文：http://blog.csdn.net/qq550764107/article/details/21299245